To produce precise printed circuits directly on nondevelopable three-dimensional surfaces, it is possible to use the method described in the documents U.S. Pat. No. 4,738,746, EP-0 241 331 and FR-2 596 230. This method starts with said surface, although three-dimensional nondevelopable, being uniformly covered with a layer of an electrically conductive material, which is in turn covered with a layer of a protective material. After said layers of conductive material and protective material have been formed, the outline of said patterns is mechanically traced by means of a tool cutting grooves, the depth of which is at least equal to the thickness of said protective layer, and then said layers are subjected to the action of a chemical capable of selectively etching said electrically conductive material without etching said protective material, this chemical etching operation being continued for a time long enough for said electrically conductive material to be removed over its entire thickness plumb with said grooves, after which those parts of said layer of electrically conductive material external to said patterns are separated from the substrate by peeling.
Thus, thanks to the above method, it is possible for electrically conducting patterns to be produced directly on three-dimensional nondevelopable surfaces without having to use a mask or an auxiliary substrate, with which mask or substrate it would moreover be technically difficult to obtain such precise patterns both as regards their shape and their position on said surfaces.
In such a prior method, to trace the outlines of the electrically conducting patterns, a tool provided with at least one etching tip or with at least one cutting blade is used, said tool being mounted in a machine (for example a five-axis numerical-control machine) charged with moving it relative to the nondevelopable surface.
In this way it is possible to produce devices having a nondevelopable surface bearing electrically conducting patterns in an easy and precise manner. For example, by implementing this known method it is possible to produce high-quality grid reflectors capable of working in the Ku band (11 to 18 GHz) and formed from at least one array of parallel conducting wires, these conducting wires having a width of 0.25 mm and a thickness of 35 microns and being distributed with a 1 mm pitch on a surface at least approximately in the form of a paraboloid, the opening diameter of which may be up to 2300 mm.
However, this prior method has technical and economic limitations. For example, if instead of a grid reflector intended to work in the Ku band it is desired to produce such a reflector intended for the Ka band (20 to 30 GHz), the width, the thickness and the distribution pitch of the conducting wires become much smaller (for example, 0.125 mm, 18 microns and 0.5 mm respectively) and difficulties arise due to the smaller width and smaller thickness of the conducting wires and of the inter-wire regions, namely:                the conducting pattern tracing parameters (pressure and arrangement of the etching tips or blades) and the chemical etching parameters (time) become very sensitive, thus resulting in geometrical defects and embrittlement of the conducting wires during peeling;        when tracing the conducting wires, the edge effects become significant, the tips or blades pushing back, in the manner of a plow, the thinner conducting material and reducing the adhesion of the conducting wires to the substrate; and        the regions between wires are fragile and therefore liable to break during peeling.        
As a result, it is necessary to ensure that the tracing by the tool is always perfect and that the execution of the method has to be slowed down, thereby increasing the costs of fabricating such a reflector.
Moreover, document DE-40 10 244 A1 teaches a method for producing a printed circuit on a three-dimensional nondevelopable surface. In this method, said surface is covered uniformly with a layer of an electrically conductive lacquer and then said layer is cut with a laser to the form of the printed circuit. Finally, the printed-circuit blank thus formed is metallized so as to obtain the definitive printed circuit.
Thus, the method described in document DE-40 10 244 A1 makes it possible to produce printed circuit patterns without having to mechanically cut, by contacting, a layer of electrically conductive material. However, during laser ablation of the uniform layer of electrically conductive lacquer, there is a risk of said nondevelopable surface being damaged.